Reactions that release or absorb energy
Grade 10 Science Worksheet
Circle the best answer, or write your answer on the line.
An energy diagram shows the reactants at 120 kJ, the top of the hill at 180 kJ and the products at 40 kJ. What is the activation energy, Ari?
An energy diagram shows the reactants at 50 kJ, the top of the hill at 130 kJ and the products at 90 kJ. What is the activation energy, Bo?
An energy diagram shows the reactants at 200 kJ, the top of the hill at 260 kJ and the products at 150 kJ. What is the activation energy, Esme?
H₂ + Cl₂ → 2 HCl has ΔH = −184.6 kJ. What is ΔH for 2 HCl → H₂ + Cl₂, Jun?
- −184.6 kJ
- +184.6 kJ
- 0 kJ
Melting ice absorbs heat. What sign does ΔH have when water freezes, Kira?
- Zero: it stays at 0 °C
- Negative: freezing releases heat
- Positive: freezing absorbs heat
In a reusable hand warmer, sodium acetate crystallizing is exothermic. What happens when it is reheated to redissolve, Luz?
- It releases heat
- No heat moves
- It absorbs heat
Where does an instant cold pack get the heat it absorbs, Milo?
- From the skin and surroundings
- From the empty air inside it
- From the ammonium nitrate itself
Ammonium nitrate dissolves and the water cools from 24.9 °C to 20.3 °C. Is the dissolving exothermic or endothermic, Pia?
- Exothermic: the solid vanished
- Endothermic: the water cooled
- Exothermic: the water cooled
On an energy diagram, what does a catalyst change, Ren?
- It changes ΔH
- It lowers the hill
- It raises the products
Reaction A has ΔH = −50 kJ and reaction B has ΔH = −200 kJ. Which releases more heat, Zee?
- Reaction A
- Reaction B
- They release the same